Neuroscience: Brain Functions and Anatomy

Neurological Bases of Speech and Language

• The presentation is about the neurological bases of speech and language.
• The presentation covers the objectives, introduction to the topic, the central nervous system (neurons), the central nervous system components, brain functions, the Cerebrum, and its structure, the Cerebellum, language and communication, cognition and higher functions, memory, brain maturation, language processing, language comprehension, language production, and conclusion.

Objectives

• Understand the structures and functions of the brain in relation to language.
• Describe basic brain functions.
• Describe the major brain areas responsible for linguistic processing.
• Outline major theories of brain lateralization.
• Describe models to understand linguistic processing.

Introduction

• Describing how brains process language is the focus of neurosciences.
• Neuroscience observes both neuroanatomy (where brain structures lay) and neurophysiology (how brains function).
• Neurolinguistics is the study of neuroanatomy, physiology, and biochemistry of language; connecting neurology and linguistics.
• Neurolinguists identify structures in the nervous system engaged in language processing and aim to explain the process.

Central Nervous System (Neurons)

• Neurons are basic units of the nervous system.
• A nerve is a collection of neurons, containing approximately 100 billion neurons.
• Neurons have three parts: a cell body (carrying genetic information, maintaining structure, and providing energy), axons (transmitting impulses away from the cell body), and dendrites (receiving and transmitting impulses to the cell body).
• Axon lengths vary from 1 millimeter to 1 meter.
• Impulses "jump" the synapse (a minuscule space).

Central Nervous System: Components

• The nervous system comprises the brain, spinal cord, and associated nerves and sense organs.
• The central nervous system (CNS) comprises the brain and spinal cord, controlling and coordinating body functions.
• The peripheral nervous system (PNS) exists outside the CNS, carrying signals to and from the CNS and the rest of the body through nerves.
• The PNS contains 12 cranial nerves and 31 spinal nerves that interact with the CNS.
• Most (approximately 85%) of the nervous system's neurons are in the CNS.

Brain Functions

• Three main brain functions: Regulation, Processing, and Formulation.

• Regulation: Located in the reticular formation of the brainstem, responsible for energy level and overall cortex tone, aiding the functioning of other brain processes, and enabling the brain to effectively monitor, evaluate, and adjust behaviors.

• Processing: Located in the posterior portion of the cortex; responsible for analyzing sensory information, coding, storing, and synthesizing information. Distinct specialized areas process information based on sensory input.

• Formulation: Located in the frontal lobe; involved in planning, intentions, and regulating attention and concentration for complex behavior and motor functions.

Brain - Cerebrum

• The cerebrum is the large, prominent part of the brain, comprising 40% of the brain's total weight.
• It is responsible for higher cognitive functions, sensory perception, and voluntary motor control.
• Divided into left and right hemispheres, interconnected by the corpus callosum.

Brain - Cerebrum: Structure

• Cerebral Cortex: Outer layer of the cerebrum, increasing surface area, and divided into four lobes (frontal, parietal, temporal, and occipital), each with specific functions. Key areas include the primary motor cortex (frontal lobe) and sensory cortex (parietal lobe).
• Subcortical Structures:
• Basal Ganglia: Involved in motor control and procedural learning.
• Limbic System: Involved in regulating emotions (hippocampus, amygdala, and hypothalamus).
• Thalamus: A relay station for sensory information.
• Cerebral Hemispheres: Divided into left and right hemispheres, connected by the corpus callosum, showing lateralization (left hemisphere linked to language, right to spatial skills).

Brain - Cerebrum Functions

• Motor Functions: Primary Motor Cortex (initiates voluntary movements), Premotor Cortex (plans and coordinates complex movements), and Supplementary Motor Area (involved in motor planning & execution).
• Sensory Functions: Primary Sensory Cortex (receives and processes sensory info), Somatosensory Cortex (processes tactile/proprioceptive info), Visual, Auditory, and Olfactory Areas (process respective sensory inputs).

Language and Communication

• Broca's Area: Involved in speech production (frontal lobe).
• Wernicke's Area: Responsible for language comprehension (temporal lobe).
• Arcuate Fasciculus: Connects Broca’s and Wernicke’s areas to facilitate language processing.
• Prefrontal Cortex: Involved in executive functions, decision-making, and personality.
• Association Areas: Integrate sensory information for complex cognitive processes.

Memory

• Hippocampus: Crucial for forming and consolidating declarative memories.
• Amygdala: Involved in emotional memory and processing.
• Limbic System: Plays a key role in emotional regulation.

Brain - Cerebellum

• The cerebellum is the "little brain," involved in motor coordination, balance, and certain cognitive functions.
• Its structure consists of two hemispheres connected by the vermis.
• The cerebellar cortex (the outer layer) has a large surface area for neural connections.

Learning and Memory

• The cerebellum contributes to motor learning and skilled movements.
• Research also indicates the cerebellum's involvement in non-motor learning and memory tasks.

Brain - Cerebellum: Connections and Functions

• The cerebellum communicates with the brainstem.
• Its role includes coordinating and controlling involuntary functions (heartbeat, breathing), motor control, and certain aspects of cognitive function.

Hemispheric Asymmetry

• Also known as cerebral lateralization, this refers to the functional and structural differences between the brain's left and right hemispheres.
• Specialized functions are often assigned (lateralized) to one hemisphere (e.g., speech and language function to left, spatial functions to the right).
• The hemispheres are complementary, working together through communication pathways.

Hemispheric Asymmetry: Structural Differences

• Corpus Callosum: A thick bundle of nerve fibers connecting the two hemispheres to facilitate communication.
• Sylvian Fissure: The deep groove separating the temporal lobe from the frontal and parietal lobes, with asymmetrical extensions in some cases.

Evidence of Hemispheric Asymmetry

• Split-Brain Studies: Research on patients with severed corpus callosum (used to treat epilepsy) demonstrates each hemisphere’s independent function in certain tasks.
• Functional Brain Imaging: Neuroimaging techniques (like fMRI, PET) reveal that specific tasks activate certain hemispheres, showing specialization.

Right Hemisphere

• Specialized in holistic processing, including visuospatial processing (space, depth orientation, and face recognition), as well as in understanding language (specifically prosody, emotional expression, abstract language, and some forms of figurative language).
• Processes printed words but struggles with decoding information based using grapheme-phoneme (letter-sound) correspondence.
• Crucial for emotional processing, integration of different sensory information, and recognizing environmental sounds.

Left Hemisphere

• Specialized for language in all forms (oral, written, visual), linear order perception, mathematical and logical reasoning.
• More adept at step-by-step processing of information.
• Handles acoustic analysis of speech (e.g., recognizing phonemes).
• Demonstrates auditory comprehension in young children.

Variation

• Left and right hemispheres are different, and have different abilities, but work together/collaborate.

Brain Maturation

• Language development is closely related to brain maturation and specialization (brain weight and organization change over time).
• Gross brain weight changes significantly during the first two years of life, and this rapid change is a critical element of brain development.

Language Processing

• Language and speech locations in the brain are difficult to pinpoint definitively.
• Language processing involves several overlapping areas, not a single designated area, and many different interconnected parts of the brain.
• Brain imaging (monitoring cerebral blood flow) helps solidify the understanding of the specific linguistic areas involved.
• The earlier assumption that language processing occurs in a linear fashion (sequential, phonetic, phonological, grammatical, and semantic) is not entirely accurate. Instead, the system is far more intricate.

Language Comprehension

• Comprehension is a complex cognitive process.
• Involves different parts of the brain working together; including the collaboration of different brain regions dedicated to the processing of auditory information and language decoding.
• Auditory processing: Initial phase of comprehension, focusing on incoming signals.
• Language decoding: Identifying and understanding the meaning of interpreted information, using language, semantic, and contextual cues.
• Attention allocation: Brains must prioritize information given the limited capacity for processing information.
• Location in the brain: Auditory signals are initially received in the brainstem, then relayed to Heschl’s area in the auditory cortex.
• Further linguistic processing: linguistic information (especially significant elements) are routed to the left temporal lobe for analysis.
• Paralinguistic processing: Elements like intonation, rate, and rhythm are also processed, this time to the right temporal lobe, and this distinguishes between linguistic and paralinguistic components.
• Phonological analysis begins in Heschl's area.
• Memory storage and consolidation relies on both the right and left hemisphere, with word meanings stored diffusely and concepts more locally, within the temporal lobe.

Language Comprehension: Location

• Pathway from brainstem to Heschl’s area: Auditory signals are received in the brainstem and relayed to Heschl's area (in each auditory cortex), with 60% of these signals coming from the opposite side of the body.
• Role of Heschl's area: plays a key role in distinguishing between linguistic and non-linguistic noise.

Language Comprehension: Linguistic Processing and Memory

• Linguistic analysis: Significant incoming information is processed.
• Paralinguistic processing: elements are routed to the right temporal lobe.
• Initiation of phonological analysis: Heschl’s area is a starting point for analyzing incoming linguistic information
• Auditory working memory: involved in holding information for analysis of linguistic units that are longer than a few words.

Language Comprehension: Linguistic Processing and Memory (continued)

• Broca's Area and Syntax Processing: Attending to syntax, processing discrete linguistic units, and analyzing phonological information from Heschl's area--plays a key role in executive functions and contributes to reasoning and planning.
• Wernicke's Area and Linguistic Analysis: Incoming information in working memory undergoes linguistic analysis in Wernicke’s area (left temporal lobe). Phonological and syntactic analyses are completed in this area.

Language Comprehension: Processing

• Automatic speech processing: Well-rehearsed speech is usually processed in the right hemisphere. Whole units are processed.
• Angular and Supramarginal Gyri: Play a crucial role in processing, integrating linguistic with other input (visual, auditory, tactile).
• Multimodality Input and Late Myelination: Late myelination of angular and supramarginal gyri underlines their role in the complexity of linguistic processing, incorporating multimodal input in language processing.
• semantic analysis and distribution: semantic information is distributed throughout the brain, often with the frontal lobe directing and evaluating. Wernicke's area performs a primary analysis.
• Right hemisphere involvement: Involved in the interpretation of figurative, abstract, and non-literal language.
• Word recognition and semantic decoding: right hemisphere plays a key role in word recognition, alongside paralinguistic processing; helps distinguish between ambiguous input.
• Memory and consolidation: Information is stored in the temporal lobe (primarily) but also throughout cortex; hippocampus in left temporal lobe helps consolidate memory.

Language Comprehension: Processing (Continued)

• Pragmatic Analysis and Social Awareness: Frontal lobe, in combination with the right hemisphere (paralinguistic information), helps complete pragmatic analyses and understanding intent.

Conclusion

• The interplay of Broca's, Wernicke's areas, and the frontal lobe's executive functions helps orchestrate language processing.
• The angular and supramarginal gyri, and their late myelination contribute to the integration of multimodal input (word recall and longer syntactic units) and comprehension.
• The complexity of language comprehension requires the understanding of the interplay of both hemispheres, memory consolidation, and pragmatic analysis.

Language Production

• Speech production involves multiple, overlapping brain regions, especially Broca's area.
• Broca's area is a crucial area for speech motor programming, preparing and coordinating speech motor programs for speech signals.
• fMRI studies during speech production and observation highlight activity in Broca's area.
• Other areas of the cortex play a role in the execution of speech movements.
• The interplay between Broca’s area's involvement in motor production and phonological analysis shows a core link.
• Analogous to Broca's area, there are activities in the right hemisphere that may be similar in their functions.
• Language production involves several brain areas and interactions, emphasizing the integrated and sophisticated nature of this process.

Language Production: Location

• Production and comprehension functions often share general brain areas, emphasizing the integrated nature of language processing.
• Conceptual basis formation: Concepts associated with the message originate in memory areas in the cortex.
• Organization in Wernicke's area: Wernicke's area is instrumental in organizing the underlying structure of a message to be communicated, facilitating effective communication.

Language Production: Transmission and Processing

• Transmission through the arcuate fasciculus: The arcuate fasciculus transmits the organized message from Wernicke’s area to Broca’s area.
• Broca’s area in the frontal lobe: Broca’s area receives the message and activates the motor program for language production.
• Transformation of the message: Transforming abstract concepts into specific forms involves complex brain pathways.
• Exner’s area and writing activation: Exner’s area, analogous to Broca's area, plays a vital role in activating the muscles associated with writing.
• Broca’s area and motor program coordination: Broca’s area takes charge of coordinating the motor program in order to verbalize the message, with motor signals travelling to specific motor cortex areas resulting in speech production (respiration, phonation, resonation, and articulation).

Language Production: Effects of Damage

• Damage to key language areas, including Broca’s, Wernicke’s and arcuate fasciculus affect speech production and reception, sometimes more subtly in terms of clarity (coherence).
• Difficulties may include the physical production of speech, comprehension of language, or both.

Language Production: Overview

• Language production is not a linear process.
• Several areas work together, highlighting the intricate and multifaceted nature of language processing; models of how this process works have been proposed to aid in our understanding.

Language Production: Conclusion

• There is significant processing and collaboration between different brain regions; notably the areas mentioned above.
• Speech production engages a network of brain regions (including Broca's area, memory areas, Wernicke’s area, arcuate fasciculus, frontal lobe).
• Damage to language areas has varied effects; highlighting the specialized roles of Wernicke's area, the arcuate fasciculus and Broca's area, and thereby emphasizing the interplay.

Explore the intricate functions and anatomy of the brain with this quiz. It covers topics such as cranial nerves, cognitive functions, and language processing areas. Test your knowledge on how various brain regions contribute to behavior and cognition.